Preparation of galactans from Gracilaria debilis and Gracilaria salicornia (Gracilariales, Rhodophyta) of Indian waters

Abstract

Superior quality non-methylated and low-sulphated galactans were extracted from two Indian agarophytes namely Gracilaria debilis and G. salicornia growing naturally along the west coast of India, using an eco-friendly method developed in our laboratory. The galactans were characterised by FT-IR, 13 C NMR, GC-MS, ICP, GPC and rheological measurements. G. debilis produced exclusively nonmethylated galactan exhibiting the greatest gel strength of 650±25 g cm −2 and lowest sulphate of 0.21±0.06%. On the contrary, G. salicornia polysaccharide was composed of nonmethylated galactose (major) and mannose (minor), having gel strength of 510±25 g cm −2 and sulphate of 0.45±0.06%. Very low heavy metal contents were determined in both the galactan samples, which may thus be potentially useful in food and biological applications.

Growth and biochemical characterization of green and red strains of the tropical agarophytes Gracilaria debilis and Gracilaria edulis (Gracilariaceae, Rhodophyta)

“…The maximum gel strength (800 g cm −2 ) recorded in G. debilis was higher when compared with the previous reported values in G. debilis (335 g cm −2 , (Duckworth et al 1971; 650 g cm −2 , Mehta et al 2010). When comparing alkali treated other Indian agarophyte data (Meena and Siddhanta 2006), the maximum gel strength value of G. debilis was similar to that reported in Gelidiella acerosa (800 g cm −2 ) and Gracilaria crassa (800 g cm −2 ) and was higher than G. edulis (450 g cm − 2 ), G. corticata (100 g cm −2 ), and G. fergusonii (135 g cm −2 ).…”

“…The agar from G. debilis is capable of forming a firm gel before treatment with alkali and had a significant amount of polysaccharide eluted in the water fraction and a lower sulfate content (0.8 %) which responsible for high gel strength agar (Duckworth et al 1971). 13 C NMR spectra of G. debilis agar confirmed that it is the presence of non-methylated polysaccharides which is responsible for high gel strength (Mehta et al 2010).…”

“…Mariculture technology for G. edulis has been successfully developed, with more recent efforts on seedling production for year-round farming (Ganesan et al 2011;Ashok et al 2016). Gracilaria debilis (Forsskål) Børgesen is yet another agarophyte which produces non-methylated galactan exhibiting comparatively high gel strength of 650 g cm −2 (Mehta et al 2010). Cultivation of this alga was attempted earlier in Barbados, West Indies (Goldstein 1973).…”

Isolation and physico-chemical characterisation of extracellular polymeric substances produced by the marine bacteriumVibrio parahaemolyticus

“…The EPS were hydrolysed in 2.0 M H 2 SO 4 (1008C, 6-8 h), and sugar was converted to alditol acetates by reduction followed by methylation (Mehta et al 2010). Alditol acetates were analysed and quantified on a GCMS-QP2010 (Shimadzu, Japan) using an SGE BP-225 capillary column (25 m length, 0.22 mm diameter and 0.25 mm thickness).…”

Preparation and functional evaluation of agarose derivatives

“…Gel strength was measured in 1% (w/v) gel of modified Ag products and 1% (w/v) gel of the parent Ag at 20°C on a Nikkansui‐type gel tester (Kiya Seisakusho Ltd., Japan). Gelling and melting points were recorded following the reported method . Apparent viscosity was measured (in 1% w/v sample) on a Brookfield viscometer (DV‐II +Pro), using SC4–18 spindle at 60 rpm at 80°C.…”